Electrochemical analyte

Abstract

An electrochemical analyte sensor formed using conductive traces on a substrate can be used for determining and/or monitoring a level of analyte in in vitro or in vivo analyte-containing fluids. For example, an implantable sensor may be used for the continuous or automatic monitoring of a level of an analyte, such as glucose, lactate, or oxygen, in a patient. The electrochemical analyte sensor includes a substrate and conductive material disposed on the substrate, the conductive material forming a working electrode. In some sensors, the conductive material is disposed in recessed channels formed in a surface of the sensor. An electron transfer agent and/or catalyst may be provided to facilitate the electrolysis of the analyte or of a second compound whose level depends on the level of the analyte. A potential is formed between the working electrode and a reference electrode or counter/reference electrode and the resulting current is a function of the concentration of the analyte in the body fluid.

We claim: 
     
       1. An analyte responsive electrochemical sensor comprising a working electrode and a mass transport limiting membrane, which mass transport limiting membrane maintains a rate of permeation of the analyte through the mass transport limiting membrane with a variation of no more than 3% per ° C. at temperatures ranging from 30° C. to 40° C. 
     
     
       2. The electrochemical sensor of claim 1, wherein a rate of permeation of the analyte through the mass transport limiting layer varies by no more than 1% per °C. for temperatures ranging from 30° C. to 40° C. 
     
     
       3. The electrochemical sensor of claim 1, wherein the mass transport limiting layer comprises a membrane having a plurality of track etched pores. 
     
     
       4. The electrochemical sensor of claim 1, wherein the mass transport limiting layer absorbs 5 wt. % or less of water at 37° C. when in contact with interstitial fluid for 24 hours. 
     
     
       5. An electrochemical sensor, comprising: a substrate; and   a working electrode disposed on the substrate, the working electrode comprising a carbon material and having a width along at least a portion of the working electrode of 150 μm or less.   
     
     
       6. The electrochemical sensor of claim 5, further comprising a catalyst for catalyzing a reaction of an analyte, the catalyst being disposed proximate to the working electrode. 
     
     
       7. The electrochemical sensor of claim 6, wherein the catalyst is disposed on the working electrode. 
     
     
       8. The electrochemical sensor of claim 6, further comprising an electron transfer agent disposed on the working electrode. 
     
     
       9. The electrochemical sensor of claim 8, wherein at least a portion of the catalyst is in contact with the electron transfer agent. 
     
     
       10. The electrochemical sensor of claim 6, wherein the catalyst is nonleachably disposed within the electrochemical sensor. 
     
     
       11. The electrochemical sensor of claim 6, wherein the catalyst is immobilized within the electrochemical sensor. 
     
     
       12. The electrochemical sensor of claim 6, wherein the catalyst comprises an enzyme. 
     
     
       13. The electrochemical sensor of claim 12, wherein the enzyme is an oxidase or a dehydrogenase. 
     
     
       14. The electrochemical sensor of claim 13, wherein the analyte is glucose and the enzyme is oligosaccharide dehydrogenase, PQQ-glucose dehydrogenase, or glucose oxidase. 
     
     
       15. The electrochemical sensor of claim 6, further comprising a second catalyst for catalyzing a reaction of a product compound formed in the reaction of the analyte. 
     
     
       16. The electrochemical sensor of claim 15, wherein the product compound comprises hydrogen peroxide and the second catalyst comprises a peroxidase. 
     
     
       17. The electrochemical sensor of claim 5, wherein the substrate is flexible. 
     
     
       18. The electrochemical sensor of claim 5, wherein a width along at least a portion of the working electrode is 75 μm or less. 
     
     
       19. The electrochemical sensor of claim 5, wherein a width along at least a portion of the working electrode is 25 μm or less. 
     
     
       20. The electrochemical sensor of claim 5, wherein the substrate is flexible. 
     
     
       21. The electrochemical sensor of claim 5, further comprising a second electrode disposed next to the working electrode, the second electrode and working electrode being disposed 150 μm or less apart. 
     
     
       22. The electrochemical sensor of claim 5, wherein the working electrode is disposed in a recessed channel formed on a surface of the substrate. 
     
     
       23. The electrochemical sensor of claim 5, wherein the working electrode is formed by transferring, to the substrate, carbon material electrically attracted to a drum in an image of the working electrode. 
     
     
       24. The electrochemical sensor of claim 5, wherein the working electrode is formed by transferring, to the substrate, carbon material magnetically attracted to a drum in an image of the working electrode. 
     
     
       25. The electrochemical sensor of claim 5, wherein the working electrode is formed by transferring the carbon material from a film onto the substrate using a print head. 
     
     
       26. The electrochemical sensor of claim 5, wherein the working electrode is formed by ejecting carbon material onto the substrate. 
     
     
       27. The electrochemical sensor of claim 5, wherein the working electrode is formed by depositing a curable coating on the substrate, curing portions of the curable coating to form a channel, and depositing carbon material in the channel to form the working electrode. 
     
     
       28. An electrochemical sensor, comprising: a substrate;   a conductive material disposed on the substrate to form a working electrode;   catalyst dispersed in the conductive material, the catalyst catalyzing a reaction of the analyte to generate a signal at the working electrode; and   a binder dispersed in the conductive material wherein the binder is cured so that the catalyst and conductive material are non-leachably disposed on the substrate.   
     
     
       29. An implantable electrochemical sensor, comprising: a substrate having a longitudinal axis with a narrow distal region that is configured and arranged for implantation into an animal and a wider proximal region that extends in a single lateral direction from the longitudinal axis;   at least one working electrode disposed on the narrow distal region of the substrate; and   at least one contact pad disposed on the wider proximal region of the substrate and in electrical communication with a one of the at least one working electrodes.